Bug 15672 – kernel patch for gcc 3.2 optimizations

• Product: Gentoo Linux
• Status: RESOLVED INVALID

[Description Chris PeBenito (RETIRED) 2003-02-13 23:35:59 UTC]

Here is a kernel patch, which adds gcc3 optimizations to the kernel build.  It
is similar to the gcc31-compile-optimizations patch used in gentoo-sources.  It
adds these options to the Processor type selection:

6xx(GCC>3.1)
7xx(GCC>3.1)
74xx(GCC>3.1)
7450(GCC>3.1)

When one of these are selected, -O3 is added to CFLAGS and the appropriate -mcpu
setting.  This is a start, with testing more optimization flags could be added
if you're daring :).  Obviously this needs some testing more testing, but as of
this writing, its working fine on my G3 so far.

[Comment 1 Chris PeBenito (RETIRED) 2003-02-13 23:36:46 UTC]

Created attachment 8268 [details, diff]
gcc31-compile-optimizations-ppc kernel patch

[Comment 2 Chris PeBenito (RETIRED) 2003-02-13 23:39:52 UTC]

I forgot to mention that it applies cleanly to 2.4.20: vanilla and ppc-sources-r3

[Comment 3 Chris PeBenito (RETIRED) 2003-02-16 12:55:39 UTC]

Created attachment 8335 [details, diff]
gcc31-compile-optimizations-ppc kernel patch

There was an error in the previous patch, causing the option MPC8260 CPM
Support to not show up, this should fix it.

[Comment 4 Bryon Roche (RETIRED) 2003-04-28 11:55:56 UTC]

I'll bang around with this and see if it works on my G4, but I kind of doubt that it will.

[Comment 5 Pieter Van den Abeele (RETIRED) 2003-07-15 01:06:43 UTC]

Patch seems ok to me, my only comment is that -O3 on a G4 is known to be flaky.
Apart from that it is a non-exclusive patch (meaning, you can still compile the kernel the old way if you prefer).

If we switch to -O3 only for G3, this patch is ok for inclusion if kain wants to.





 

[Comment 6 Jay Pfeifer (RETIRED) 2003-09-16 11:21:22 UTC]

I would strongly discourage -O3 for any kernel compiles. I know firsthand it 
can cause issues in some inline assembler and some other code. AC has voiced 
his concern on this a couple of times as well as a few others in LKML. 
 
I already removed the -O3 opts from Gentoo Sources ~ 6 months ago. Closed a 
good number of bugs. 
 
Jay 

[Comment 7 Chris PeBenito (RETIRED) 2003-09-17 07:39:58 UTC]

This should probably be closed out, and the patch not used.  I made it 8 months ago.  I dont think it will apply to recent benh kernels.  It probably doesnt do much for ppc anyway, esp. since it should be -O2 (as Jay pointed out) instead of the -O3 I did back then.

[Comment 8 Tim Yamin (RETIRED) 2003-09-17 11:58:00 UTC]

Closed as requested.